Method and device for cryogenic freezing of products
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Solution Overview
Problem
Existing cryogenic freezing technologies face challenges with uneven freezing due to belt slippage and deformation, leading to variable passage time and immersion depth, and high cryogen losses through inefficient impregnation methods.
Innovation Solution
The implementation of successive cryogenic liquid containers positioned under the conveyor belt, allowing the belt to pass flush over the liquid surface, with regulated liquid levels to maintain consistent immersion and reduce cryogen consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the polymer conveyor belt is immersed in a bath of liquid nitrogen, then the freezing effectiveness is improved, but the belt deforms due to bubble formation and tension, causing uneven immersion depth
Solution Approach 1:
Instead of immersing the belt in a bath of liquid nitrogen, the invention inverts the approach by positioning the belt above the bath and allowing liquid nitrogen to rise and contact the belt from below. This eliminates the deformation caused by immersion while maintaining effective heat transfer for freezing.
Solution Approach 2:
The invention introduces an intermediary structure (the bath container positioned below the belt) that mediates between the liquid nitrogen and the conveyor belt. This allows heat transfer to occur through the belt material without direct immersion, preventing bubble-induced deformation while maintaining freezing effectiveness.
2Manufacturing precision
If the conveyor belt speed is not well controlled, then the passage time through the freezer becomes variable, but maintaining precise speed control increases device complexity
Solution Approach 1:
The invention makes the system self-regulating by designing the belt drive and bath positioning such that the passage time is inherently controlled by the mechanical configuration rather than requiring complex active control systems. The belt speed and immersion depth are coupled through the mechanical design, allowing the system to self-regulate.
3Manufacturing precision
If the liquid nitrogen bath level is not maintained, then the immersion depth becomes variable affecting freezing quality, but continuous level monitoring and adjustment increases energy consumption
Solution Approach 1:
The invention implements a feedback mechanism where the bath level is monitored and automatically adjusted to maintain consistent immersion depth. The level sensor detects variations and triggers liquid nitrogen replenishment only when needed, ensuring precise immersion control while minimizing unnecessary energy consumption from continuous operation.
4Temperature
If spray or soaking methods are used to impregnate the mat with cryogen, then the freezing capability is enhanced, but cryogen losses increase significantly
Solution Approach 1:
The invention applies partial impregnation rather than complete saturation of the belt with liquid nitrogen. By positioning the belt above the bath and allowing controlled contact, the system achieves sufficient freezing capability through the portion of the belt that contacts the cryogen, significantly reducing overall cryogen consumption compared to complete soaking or spray methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures consistent freezing treatment and reduces cryogen consumption by approximately one-third, maintaining the quality of the freezing process while minimizing turbulence and cryogen loss.
Implementation Method 1
the size of the pores of the conveyor belt is such that cryogenic liquid can be retained therein, so as to ensure the total or partial freezing of the article by thermal transfer between the article and the cryogenic liquid retained in the porous substrate
Implementation Method 2
the conveyor must pass flat in this bath, at a substantially constant distance from the surface. of the bath. Thus, whatever the time of day, whatever the position of the products, they all receive the same heat treatment because they are immersed in liquid nitrogen in a substantially identical manner.
Data Source
AI summary
A device for the total or partial freezing of articles, comprising a conveyor made of a porous material insulated by an enclosure, as well as means for impregnating said conveyor with a cryogenic liquid, and means for placing articles to be frozen on the porous conveyor, characterized by the implementation of the following measures: - it comprises one or more successive containers, capable of containing the cryogenic liquid, for example liquid nitrogen, positioned under the porous conveyor, and downstream of the zone of the means for depositing the articles to be frozen on the conveyor. - it comprises means for regulating the level of liquid in the container or containers, to allow the conveyor, where the articles to be treated are arranged, to be able to pass over the successive container or containers, and be flush with the surface of the cryogenic liquid.